Rechargeable electrochemical battery cell

ABSTRACT

Rechargeable lithium battery cell having a housing, a positive electrode, a negative electrode and an electrolyte containing a conductive salt, wherein the electrolyte comprises SO2 and the positive electrode contains an active material in the composition LixM′yM″z(XO4)aFb, wherein
     M′ is at least one metal selected from the group consisting of the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn,   M″ is at least one metal selected from the group consisting of the metals of the groups II A, III A, IV A, V A, VI A, IB, IIB, IIIB, IVB, VB, VIB and VIIIB,   X is selected from the group consisting of the elements P, Si and S,   x is greater than 0,   y is greater than 0,   z is greater than or equal to 0,   a is greater than 0 and   b is greater than or equal to 0.

FIELD

The field relates to rechargeable lithium ion battery cells and treatedelectrodes for rechargeable battery cells and methods thereof.

BACKGROUND

It is well known that conventional rechargeable lithium ion batterycells have a history of safety problems. These safety problems arecaused, in part, by the organic solvent electrolyte in such batterycells, which is flammable. Because of this danger, conventionalrechargeable lithium ion battery cells contain components designed toactivate in the event of cell failure in order to prevent combustion ofthe organic solvent electrolyte. However, these components lead to, forexample, increased manufacturing costs and increase the volume andweight of the cell.

SUMMARY

In an embodiment, the positive electrode comprises an active material, acurrent collector and optionally a binder and/or conductive agent (toimprove conductivity). In a further embodiment, the negative electrodecomprises an active material, a current collector and optionally abinder and/or conductive material. In a further embodiment, the positiveelectrode and/or negative electrode are treated to reduce capacity lossdue to formation of stable covering layers on the positive and negativeelectrodes (for example, SEI layers).

In an embodiment is provided a battery cell, comprising: a housing, apositive electrode, a negative electrode and an electrolyte, wherein theelectrolyte comprises SO₂ and a conductive salt, wherein the positiveelectrode comprises a compound of the formula Li_(x)M′_(y)(XO₄)_(a)F_(b)(I) as defined herein, wherein the positive electrode further comprisesa current collector having a first portion comprising a porous metalwhich has a first and second surface and a thickness located therebetween and comprises a plurality of pores containing the compound thatextend at least partially through the thickness, wherein at least someof the pores have void spaces accessible to the electrolyte and whereinthe battery cell is a rechargeable lithium ion battery cell.

In a further embodiment is provided a battery cell, comprising: ahousing, a positive electrode, a negative electrode and an electrolyte,wherein the positive electrode comprises LiFePO₄ which is optionallydoped, wherein the electrolyte comprises SO₂ and a conductive salt,wherein the positive electrode further comprises a current collectorhaving a first portion comprising a porous metal which has a first andsecond surface and a thickness located there between and comprises aplurality of pores containing the compound that extend through thethickness, wherein at least some of the pores have void spacesaccessible to the electrolyte and wherein the battery cell is arechargeable lithium ion battery cell.

In a further embodiment is provided a battery cell, comprising, ahousing, a positive electrode, a negative electrode and an electrolyte,wherein the positive electrode comprises LiFePO₄ which is optionallydoped, the electrolyte comprises SO₂ and a conductive salt, wherein theSO₂ is in an amount greater than 40 weight percent of the weight of theelectrolyte and wherein the battery cell is a rechargeable lithium ionbattery cell.

In a further embodiment is provided a battery cell comprising a housing,a positive electrode, a negative electrode and an electrolyte, whereinthe positive electrode comprises LiFePO₄ which is optionally doped,wherein the electrolyte comprises SO₂ and a conductive salt, whereinorganic material is in an amount less than 60 weight percent of theweight of the electrolyte and wherein the battery cell is a rechargeablelithium ion battery cell.

In a further embodiment is provided a battery cell comprising a housing,a positive electrode, a negative electrode and an electrolyte, whereinthe positive electrode comprises LiFePO₄ which is optionally doped,wherein the electrolyte comprises SO₂ and a conductive salt, wherein theelectrolyte comprises at least 3 moles SO₂ per mole of conductive salt,and wherein the battery cell is a rechargeable lithium ion battery cell.

In an embodiment, the measurements described herein are at 20 degrees C.and 1 bar.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of a battery cell embodiment.

FIG. 2 shows a cross-sectional view of a metal foam embodiment.

FIG. 3 shows a cross-sectional view of a portion of a positive electrodeembodiment.

FIG. 4 shows a view of a porous metal current collector embodiment.

FIG. 5 shows a view of an electrode embodiment and a schematicrepresentation of the porous metal current collector portion of theelectrode filled with active material.

FIG. 6 shows a view of an embodiment showing a positive electrodecontained in a pouch faced on each side by a negative electrode.

FIG. 7 shows an embodiment of a layer for covering a plurality ofelectrodes.

FIG. 8 shows an embodiment of a prismatic housing containing a pluralityof electrodes,

FIG. 9 shows an embodiment of a prismatic housing containing a pluralityof electrodes and a top cover thereto.

FIG. 10 shows an embodiment of the top cover of a prismatic housing.

FIG. 11 shows the dependence of the discharge capacity at differentdischarge C-rates on the number of cycles for an experiment performedwith a positive electrode.

FIG. 12 shows the dependence of the discharge capacity on the dischargerate for an experiment performed with a positive electrode in comparisonwith published results.

FIG. 13 shows the dependence of the electrical resistance of anelectrode at different discharge C-rates on the number of cycles for anexperiment performed with a positive electrode.

FIG. 14 shows the dependence of the capacity on the number of cycles foran experiment performed with two different positive electrodes.

FIG. 15 shows the dependence of the capacity on the number of cycles fora further experiment performed with two different positive electrodes.

FIG. 16 shows the dependence of the discharge capacity on the number ofcycles for an experiment performed with two different positiveelectrodes.

FIG. 17 shows the dependence of the capacity on the number of cycles fora long-duration experiment.

FIG. 18 shows the dependence of the electrical voltage on the chargingcapacity for three differently treated negative electrodes.

FIG. 19 shows the percent of discharge capacity versus cycle number fordifferent molar ratios of SO₂ to conductive salt for LiCoO₂ activematerial.

FIG. 20 shows the percent of discharge capacity versus cycle number fordifferent molar ratios of SO₂ to conductive salt for LiFePO₄ activematerial.

DETAILED DESCRIPTION

As described below, embodiments of the described rechargeable lithiumion battery cell, comprise a positive electrode, a negative electrode, ahousing and an electrolyte, where the electrolyte comprises SO₂ and aconductive salt and a housing.

Positive Electrode

Positive Electrode Active Material and Other Compounds

In an embodiment, the positive electrode comprises an active materialcompound of the formula Li_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b) (Formula I). Inan embodiment M′ is at least one metal selected from the groupconsisting of the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn. In afurther embodiment M″ is at least one metal selected from the groupconsisting of the metals of the groups II A, III A, IV A, V A, VI A, IB,IIB, IIIB, IVB, VB, VIB and VIIIB, and such metals are, for example,doping metals. In an embodiment X is selected from the group consistingof the elements P, Si and S. In a further embodiment x is greater than0, y is greater than 0, z is greater than or equal to 0, a is greaterthan 0 and b is greater than or equal to 0.

In a further embodiment, the active material comprises a phosphate, andin this case X is thus phosphorus. In a further embodiment, M′ is iron.In a further embodiment, b is equal to 0 and in this case, the activematerial thus does not contain any fluorine.

In a further embodiment, the compound of formulaLi_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b) (Formula I) is LiFeM″_(z)PO₄. In afurther embodiment, the compound of formulaLi_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b) (Formula I) is LiFePO₄.

The term “at least one metal” used in Li_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b)(Formula I) means that M′ and M″ each may be two or more of therespectively defined metals. Accordingly, the recitations y and z referto the totality of metals that are recited above, respectively, by M′and M″. As an example, where M′ is two of the defined metals, in thecase, for example, where the compound of the formulaLi_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b) (Formula I) is Li₁[Fe_(m)Mn_(1-m)]₁PO₄,then 0.0≦m≦1.0, x, y and a are 1 and b and z are 0. In another aspect,where the compound of the formula Li_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b)(Formula I) is, for example, a doped LiFePO₄ compound, then thevariables in Li₁[Fe_(1-z)M″_(z)]₁PO₄, are: 0.0≦z≦1.0, x and a are 1, yis 1-z and b is 0.

In a further embodiment, where M″ is a doping metal or metals, asmentioned above, such doping metals are, for example, in an amount (eachdoping metal independently or the two or more doping metals incombination) less than or equal to 10 mole percent of the total numberof moles of M′_(y) in the compound of Li_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b)(Formula I).

In a another embodiment, the compound of formulaLi_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b) (Formula I) isLi_(x)M′_(y)(XO₄)_(a)F_(b), and the compound is optionally doped. In afurther embodiment, in a doped compound of the formulaLi_(x)M′_(y)(XO₄)_(a)F_(b), the doped metal or metals are, for example,in an amount, (each doping metal independently or the two or more dopingmetals in combination) less than or equal to 10 mole percent of thetotal number of moles of M′_(y) in the compound.

In a further embodiment, the doping metals are, for example, selectedfrom the group consisting of aluminum, magnesium, niobium, zirconium andions thereof.

In the compound of formula Li_(x)M′_(y)M″_(z)(XO₄)_(a)F_(b) (Formula I),the condition of charge neutrality is applied. That is, the sum ofpositive charges of Li, M′ and (when contained in the compound) M″ equalthe sum of the negative charges of the XO₄ and (when contained in thecompound) F.

Examples of commercially available positive electrode active materialsare listed in Table 1 below:

TABLE 1 Company Name Compound Product Name Phostech Lithium Inc. LiFePO₄Grade P1 Phostech Lithium Inc. LiFePO₄ Grade P2 Alees (Advanced LithiumLiFePO₄ LFP-NCO M121 Electrochemistry Co., Ltd.) Alees (Advanced LithiumLiFePO₄ LFP-NCO M12 Electrochemistry Co., Ltd.) Formosa Energy &Material LiFe_(x)M_((1−x))P_(y)O_(z) SFCM30050 Technology Co., Ltd.Prayon S.A. LiFeBPO₄ Lithium Boron Iron Phosphate

In a further embodiment, the active material is in the form of particlesand the mean particle size of such particles is at least 0.1 μm, atleast 0.2 μm, at least 0.5 μm, at least 1 μm or at 2 μm. In a furtherembodiment, the mean particle size is from 0.1 μm to 2 μm, 0.1 μm to 3μm, or 0.1 μm to 4 μm or from 0.2 μm to 2 μm, 0.2 μm to 3 μm, or 0.2 μmto 4 μm.

In a further embodiment, active material particles are coated with, forexample, with carbon or carbon containing materials, to, for example,increase conductivity.

In a further embodiment, the positive electrode comprises a conductiveagent compound, for example, carbon black or other carbon containingmaterials, to improve the conductivity of the active material. Forexample, in an embodiment, the active material is admixed with suchconductive agents.

In a further embodiment, the positive electrode optionally comprises abinding agent compound, for example the active material is admixed witha binding agent. In an embodiment, the binding agent is selected fromthe group consisting of: a fluorinated binding agent, THV (terpolymer oftetrafluoroethylene, hexafluoropropylene and vinylidene fluoride) andPVDF (polyvinylidene fluoride).

In a further embodiment, to increase, for example, cell cyclingstability, the positive electrode optionally comprises a lithiumhalogenide compound. For example, in an embodiment, the active materialis admixed with a lithium halogenide. In an embodiment, the lithiumhalogenide is lithium chloride.

In a further embodiment, in addition to the above described activematerial, the positive electrode optionally comprises a compoundselected from the group consisting of a conductive agent, a bindingagent, and a lithium halogenide, as described above, for example, inadmixture with the active material.

Positive Electrode Porous Metal Current Collector

In an embodiment, the positive electrode contains a current collectorwhich in whole or in part comprises a porous metal. In an embodiment,the porous metal 20 has a first and second surface (for example, a frontand a back surface as shown in FIG. 4) and a thickness d between thefirst and second surface.

In an embodiment, the porous metal comprises a plurality of pores P thatare defined by the porous metal structure 13. As shown in FIG. 4, in anembodiment, the pores P extend through the entire thickness and surfacesof the porous metal 20.

In a further embodiment, the porous metal 20 is a reticulated metal withthe reticulated metal structure defining the pores. In a furtherembodiment, the porous metal 20 is, for example, a metal foam, metalfleece, metal mesh or metal fabric. In a further embodiment, the metalis, for example, nickel or copper metal. An electron microscope image ofa porous nickel metal foam embodiment is shown in FIG. 2 and in theinsets shown in FIG. 4.

In an embodiment, the pores of the porous metal extend at leastpartially through the porous metal thickness d. In a further embodiment,the pores of the porous metal extend from at least one surface of theporous metal through at least 50 percent, at least 60 percent, at least70 percent, at least 80 percent or at least 90 percent of the porousmetal thickness d. In a further embodiment, the porous metal comprisesat least 50 percent, at least 60 percent, at least 70 percent, at least80 percent or at least 90 percent of the positive electrode thickness d.

In a further embodiment, the porous metal comprises at least 50 percent,at least 60 percent, at least 70 percent, at least 80 percent or atleast 90 percent of the current collector exterior surfaces. In afurther embodiment, the porous metal comprises at least 50 percent, atleast 60 percent, at least 70 percent, at least 80 percent or at least90 percent of the positive electrode exterior surfaces.

Exemplifications of commercially available porous metal foam embodimentsof are listed below in Table 2.

TABLE 2 Density Company Name Material (g/m²) Pore size (μm) Thickness(mm) Storck nickel 380.00 — 1.30 Nitech nickel 350.00 — 1.30 Inco nickel380.00 560.00 1.70 Inco nickel 380.00 580.00 1.70 Inco nickel 480.00580.00 1.70 Inco nickel 880.00 — 0.36 Inco nickel 1100.00 — 0.36 Alantumcopper 430.00 580.00 1.70 Alantum copper 480.00 580.00 1.70 Alantumcopper 350.00 580.00 1.70 Changsha Lyrun copper 480.00  95 ppi 1.70Changsha Lyrun nickel 480.00  95 ppi 1.70 Changsha Lyrun copper 400.00120 ppi 1.70 Changsha Lyrun nickel 480.00 120 ppi 1.70

Positive Electrode Porous Metal Current Collector Containing ActiveMaterial And Other Compounds

In a further embodiment, the pores P of the porous metal 20 containactive material and optionally the other compounds discussed above. FIG.3 shows an electron microscope image of the porous metal currentcollector portion of a positive electrode, having a thickness d andcontaining active material 15 in pores defined by the porous metalstructure 13. In FIG. 5, in the insets, are schematic representations ofthe pores of the porous metal containing active material and optionallyother compounds as described above 21. The schematic insets of FIG. 5also show void spaces 22 that are defined by the active materialcontained in the pores and are accessible to the cell electrolyte. Thatis, in an embodiment, the active material and optionally the othercompounds as described above fill pores P by, for example, adhering tothe porous metal structure 13 that defines the pores; however, theactive material and optionally the other compounds as described above donot completely occlude the pores P and instead partially occlude atleast some of the pores P thereby defining void spaces 22 that areaccessible to the cell electrolyte.

As noted above, the void spaces 22 shown in FIG. 5 are only a schematicrepresentation and do not correspond to the actual size or the preciseconfiguration of embodiments of the void spaces. For example, in anembodiment, as set forth herein, the average pore size is 580micrometers and the average pore size of void spaces contained in aporous metal filled with active material is from 50 to 80 nanometers.

The result of this embodiment is that, due to the pores in theabove-described current collector, the average distance of the activematerial to the current collector metal is decreased as compared toactive material adhered to a planar current collector metal foil.

In an embodiment, the active material and optionally the other compoundsdiscussed above, are applied (e.g., homogenously) to the porous metaland excess compounds are removed from the surface(s) of the porousmetal. The porous metal containing the compounds is then pressed. In anembodiment, the thickness of the filled porous metal (e.g., afterpressing) is no more than 50 percent or no more than 40 percent of theinitial thickness of the porous metal starting material.

In an embodiment, the active material and optionally the other compoundsare in an admixture. In a further embodiment, conductive agent is in anamount less than ten weight percent, less than seven weight percent,less than five weight percent or less than two weight percent of theweight of the porous metal portion of the electrode. In a furtherembodiment, binding agent is in an amount less than five weight percentor less than two weight percent of the weight of the weight of theporous metal portion of the electrode.

Herein, the term weight percent (wt. %) as applied to a component of acomposition refers to the weight of that component divided by the totalweight of the composition, expressed as a percentage. For example, asapplied to the above paragraph, if a solid composition is a mixture of Wgrams active material, X grams binding agent and Y grams conductiveagent in Z grams of nickel foam, then the wt. % of binding agent isgiven by:

$\frac{X}{W + X + Y + Z} \times 100.$

Thus, as used herein, the description that “the binding agent is in anamount less than ten weight percent of the weight of the porous metalportion of the electrode” means that if the total weight of the porousmetal portion of the electrode is 100 g, then the total weight of thebinding agent contained therein is less than 10 g.

As an additional example, in the context of a liquid composition, forexample, an electrolyte comprising SO₂, a conductive salt(s), and anorganic co-solvent, the description that the organic material is in anamount less than 60 weight percent of the weight of the electrolytemeans that if the total weight of the electrolyte (that is the totalweight in grams of the SO₂, conductive salt and organic solvent) is 100g then the weight of the organic co-solvent is less then 60 g.

Moreover, it will be understood that when a liquid electroytecomposition containing SO₂ is used in a sealed battery cell housing, theSO₂ may be in an equilibrium between the liquid and gas phase and therelative amounts of gas and liquid phase SO₂ may vary depending on theambient conditions. As used herein the weight percent of a component ofthe liquid electrolyte composition is calculated taking intoconsideration the total of the liquid and gas phase SO₂. Thus, theweight percent may be determined using either (i) the weights (typicallyin grams) of SO₂, conductive salt and organic solvent that were admixedto create the electrolyte or (ii) may be calculated based on an analysisof the electrolyte components in the housing, for example, by openingthe battery cell housing in an atmosphere of inert gas under pressureand measuring the molecular content of the gas and liquid containedtherein. It is further understood that the term “electrolyte” hereinrefers to an electrolyte admixture, with the meaning that, where some ofthe SO₂ is in a gas form and therefore is not functioning as anelectrolyte (in that, it is not involved in conductivity of lithiumions), the SO₂ is still to be considered as part of the electrolyteadmixture and therefore the amount of SO₂ in the “electrolyte” asapplied to a sealed battery cell refers to the total amount of SO₂therein whether in liquid or gaseous form.

In a further embodiment, the porous metal current collector comprising(for example, filled with) the active material and optionally the othercompounds discussed above, has the following ranges of porosity,loading, thickness and pore size. In a further embodiment, in the belowranges, the porosity, thickness and pore sizes are based on (but notlimited to) a porous metal current collector comprising active material(LiFePO₄), conductive agent (carbon black) and binding agent (THV) andthe loading is based on (but not limited to) the mass of active material(mg) (LiFePO₄) per unit area (cm²) of the porous metal current collectorcontaining active material, conductive agent and binding agent. In afurther embodiment, the porosity listed in the ranges below, ismeasured, for example, by mercury intrusion porosimetry.

The following are with respect, for example, to high energy cellembodiments. With regard to porosity, in embodiments, the porosity isfrom 25-30 percent, 20 to 30 percent or from 20 to 50 percent. Withregard to loading, in embodiments, loading is from 110 to 115 mg/cm², 90to 180 mg/cm² and 20 to 180 mg/cm². With regard to thickness, inembodiments, thickness is from 575 to 585 μm, 450 to 800 μm and 250 to800 μm.

The following are with respect, for example, to high power cellembodiments. With regard to porosity, in embodiments, the porosity isfrom 33 to 37 percent, 30 to 50 percent and 20 to 50 percent. Withregard to loading, in embodiments, loading is from 70 to 75 mg/cm², 20to 90 mg/cm² and 20 to 180 mg/cm². With regard to thickness, inembodiments, thickness is from 445 to 455 μm, 250 to 500 μm and 250 to600 μm.

In a further embodiment, the average pore size of the pores containingthe compounds is from 50-80 nm.

In a further embodiment, the porosity is no more than 50 percent, nomore than 50 percent, 45 percent, 40 percent, 35 percent, 30 percent, 25percent or 20 percent. In a further embodiment, thickness is at least0.25 mm, at least 0.3 mm, at least 0.4 mm, at least 0.5 mm or at least0.6 mm. In a further embodiment, loading is at least 30 mg/cm², at least40 mg/cm², at least 60 mg/cm², at least 80 mg/cm², at least 100 mg/cm²,at least 120 mg/cm² or at least 140 mg/cm².

In a further embodiment, thickness is from 0.20 mm to 1.0 mm.

In a further embodiment, the current collector comprises a secondportion, namely a connector which is electrically conductively connectedto the porous metal. In this embodiment, the connector and the porousmetal comprising the active material, and optionally the other compoundsdescribed above, comprise the electrode 35 as shown in FIG. 5.

In a further embodiment, the connector comprises a metal foil foldedover an edge of the porous metal. In a further embodiment, the connectorcomprises a metal foil band folded over the top edge of the porousmetal. In a further embodiment, a metal foil tab is attached to theband. In a further embodiment 23, a metal foil band is folded over thetop edge of the porous metal, a metal foil tab is attached to the bandand one or more wires are attached to the tab. In a further embodiment,the foil and wire comprise nickel metal.

Negative Electrode Active Material and Other Compounds

In an embodiment, the negative electrode comprises an active materialgraphite compound or another form of carbon compound that is suitablefor intercalating lithium ions as is understood by the skilled artisan.

A listing of embodiments of commercially available graphite activematerial is shown below in Table 3.

TABLE 3 Company Name Product Name Timcal SFG6 Timcal SFG44 Timcal KS4Timcal SLP50 Timcal SLP30 Timcal E-SLG5 - 07/04 Timcal E-SLX 50 - 032Timcal SFG150 Timcal KS150 Carbonix TX25 Carbonix TX20L KropfmühlGraphit SGB 25 L/99.9 Kropfmühl Graphit SGB 20 L/99.9 Kropfmühl GraphitSGB 10 L/99.9 Aschland Südchemie MCMB 6-28 Aschland Südchemie MCMB 10-28Aschland Südchemie MCMB 25-28 LICO LPG320—potato Graphite

In a further embodiment, the negative electrode optionally comprises abinding agent compound, for example the active material is admixed witha binding agent, with the binding agent being selected from the group ofbinding agents described above with respect to the positive electrode.In a further embodiment, the binding agent is in an amount no more thanfive weight percent, three weight percent or one weight percent of theweight of the porous metal portion of the electrode.

Negative Electrode Porous Metal Current Collector

In an embodiment, the negative electrode contains a current collectorwhich in whole or in part comprises a porous metal. In an embodiment,the porous metal current collector portion of the negative electrode isas described above with respect to the positive electrode.

Negative Electrode Porous Metal Current Collector Containing ActiveMaterial And Optionally Binder

In an embodiment, the porous metal current collector containing activematerial and optionally binder (for example, in admixture) is asdescribed above with respect to the positive electrode porous metalcurrent collector containing active material and optionally othercompounds.

In a further embodiment, the porous metal current collector comprising(for example, filled with) active material and optionally binding agenthas the following ranges of porosity, loading, thickness and pore size.In a further embodiment, in the below ranges, the porosity, thicknessand pore sizes are based on (but not limited to) a porous metal currentcollector comprising graphite active material and not containing abinding agent or a conductive agent and the loading is based on (but notlimited to) the mass of graphite active material (mg) per unit area(cm²) of the porous metal current collector containing the activematerial. In a further embodiment, the porosity listed in the rangesbelow, is measured, for example, by mercury intrusion porosimetry.

The following are with respect, for example, to high energy cellembodiments. With regard to porosity, in embodiments, the porosity isfrom 30-35 percent, 30-40 percent or from 30-50 percent. With regard toloading, in embodiments, loading is from 45-50 mg/cm², 25-55 mg/cm² and10-100 mg/cm². With regard to thickness, in embodiments, thickness isfrom 390-410 μm, 300-500 μm and 200-800 μm.

The following are with respect, for example, to high power cellembodiments. With regard to porosity, in embodiments, the porosity isfrom 43-47 percent, 40-50 percent and 30-50 percent. With regard toloading, in embodiments, loading is from 25-30 mg/cm², 15-35 mg/cm² and10-100 mg/cm². With regard to thickness, in embodiments, thickness isfrom 315-325 μm, 200-400 μm and 200-600 μm.

In a further embodiment, the average pore size of the pores containingthe active material and optionally the binder is from 50-90 nm.

In a further embodiment, the porosity is no more than 50 percent, 45percent, 40 percent, 35 percent or 30 percent. In a further embodiment,thickness is at least 0.2 mm, at least 0.3 mm, at least 0.4 mm, at least0.5 mm or at least 0.6 mm. In a further embodiment, loading is at least10 mg/cm², at least 20 mg/cm², at least 40 mg/cm², at least 60 mg/cm²,at least 80 mg/cm² or at least 100 mg/cm².

In a further embodiment, thickness is from 0.20 mm to 1.0 mm.

In a further embodiment, the current collector comprises a secondportion, namely a connector which is electrically conductively connectedto the porous metal. In this embodiment, the connector and the porousmetal comprising the active material, and optionally the other compoundsdescribed above, comprise the electrode 35 as shown in FIG. 5.

In a further embodiment, the connector comprises a metal foil foldedover an edge of the porous metal. In a further embodiment, the connectorcomprises a metal foil band folded over the top edge of the porousmetal. In a further embodiment, a metal foil tab is attached to theband. In a further embodiment 23, a metal foil band is folded over thetop edge of the porous metal, a metal foil tab is attached to the bandand one or more wires are attached to the tab. In a further embodiment,the foil and wire comprise nickel metal.

Electrolyte

In an embodiment, the electrolyte comprises SO₂ and a conductive saltand in a further embodiment is non-aqueous.

Regarding the conductive salt, in an embodiment, the conductive salt isselected from the group consisting of aluminates, halogenides, oxalates,borates, phosphates, arsenates and gallates of an alkali metal oralkaline earth metal. In a further embodiment, the conductive salt islithium tetrahalogenoaluminate. In yet a further embodiment, theconductive salt is lithium tetrachloroaluminate.

In a further embodiment, SO₂ is in an amount greater than 30 weightpercent, greater than 40 weight percent, greater than 50 weight percent,greater than 60 weight percent, greater than 70 weight percent, greaterthan 80 weight percent, greater than 85 weight percent, or greater than90 weight percent of the weight of the electrolyte.

In a further embodiment, in addition to SO₂, the electrolyte maycomprise one or more additional inorganic solvents, for example,sulfuryl chloride or thionlyl chloride.

In a further embodiment, the electrolyte may contain organic material,for example, one or more organic co-solvents. In such an embodiment, theorganic material is in an amount less than 50 weight percent, less than40 weight percent, less than 30 weight percent, less than 20 weightpercent, less than 15 weight percent, less than 10 weight percent, lessthan 5 weight percent, or less than 1 weight percent of the weight ofthe electrolyte. In a further embodiment, the electrolyte is essentiallyfree of organic material; that is, the electrolyte contains organicmaterial as an impurity only (for example an impurity resulting fromcarbon coating on the positive electrode active material or from othercarbon material in the electrodes, e.g., carbon black in the positiveelectrode or graphite in the negative electrode) not an additive. In afurther embodiment, the electrolyte contains no more than 500 parts permillion organic material. In a further embodiment, the organic materialcontained in the electrolyte has a flash point below 200° C., 150° C.,100° C., 50° C., 25° C. or 10° C. In a further embodiment, where theelectrolyte contains (or is admixed with) two or more organic materials,the combined organic materials have an average (calculated, for example,by weight percent) flash point below 200° C., 150° C., 100° C., 50° C.,25° C. or 10° C.

In a further embodiment, nitriles (for example, mononitriles ordinitriles) are in an amount less than 50 weight percent, less than 40weight percent, less than 30 weight percent, less than 20 weightpercent, less than 15 weight percent, less than 10 weight percent, lessthan 5 weight percent, or less than 1 weight percent of the weight ofthe electrolyte.

In a further embodiment, conductive salt is in an amount less than 70weight percent, less than 60 weight percent, less than 50 weightpercent, less than 40 weight percent, less than 30 weight percent, lessthan 20 weight percent or less than 10 weight percent of the weight ofthe electrolyte.

In a further embodiment, SO₂ plus conductive salt is in an amountgreater than 50 weight percent, greater than 60 weight percent, greaterthan 70 weight percent, greater than 80 weight percent, greater than 85weight percent, greater than 90 weight percent, greater than 95 weightpercent or greater than 99 weight percent of the weight of theelectrolyte. In a further embodiment, the electrolyte consistsessentially of SO₂ and conductive salt. That is, other than SO₂ andconductive salt, the electrolyte contains less than one weight percentof other materials.

It is understood that included in this description is the combination ofany two or more of the above weight percentages. Moreover, thisdescription in the previous sentence does not detract from the fact thatit is to be understood that embodiments herein also include any of theembodiments mentioned herein combined with any other one or moreembodiments herein mentioned.

In an embodiment, the electrolyte comprises at least 2.0 moles SO₂ permole of conductive salt. In a further embodiment, the electrolytecomprises at least 2, 2.5, 3, 3.5, 4, 4.5, 5, 5, 6, 6.5, 7, 7.5, 8, 8.5,9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16,16.5, 17, 17.5, 18, 18.5, 19, 19.5, or 20 moles SO₂ per mole ofconductive salt.

In a further embodiment, the electrolyte comprises from 2, 2.5, 3, 3.5,4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8 moles SO₂ per mole of conductivesalt to 20, 25, 30, 35, 50, 100, 150, 200, or 220 moles SO₂ per mole ofconductive salt.

In a further aspect, the maximum ratio of the moles of SO₂ per mole ofconductive salt is set by (1) the desired safety parameters of the cellor (2) the desired levels of electrolyte ionic conductivity of the cell.

In a further embodiment, the electrolyte is synthesized according to theprocess set forth in either of Tables 4 and 5 below. The processes setforth in Tables 4 and 5 are carried out in an inert gas (argon), at roomtemperature and unless otherwise stated at ambient pressure (1 bar).

TABLE 4 Drying Drying of lithium chloride 3 days/120° C./vacuum Dryingof aluminum particles 2 days/450° C./vacuum Mixing LiCl 434 g (10.3mole) (42 g/mole) AlCl₃ 1300 g (9.7 mole) (134 g/mole) Al 100 g (3.4mole) (29 g/mole) Mix well 1 mole AlCl₃ to 1.06 mole LiCl to 0.35 moleAl in glass flask with an opening to permit the escape of gas. Melting250° C. for 2 hours 350° C. for 2 hours 500° C. for 2 hours After 6hours, the opening in the flask is closed. 500° C. for 3 days FilteringCooling to 250° C. Filter through a glass fiber cloth. Introduction toThe next day the melt is cooled to room temperature. SO₂ gas The flaskwith the melt is evacuated and SO₂ is introduced up to a desired amount,to obtain a desired mole ratio of SO₂ per mole of LiAlCl₄, from acontainer containing the SO₂ under pressure. The flask is cooled whilegas is introduced. The salt melt is dissolved in the SO₂ and the liquidelectrolyte is obtained.

TABLE 5 Drying Drying of lithium chloride at 750° C. Mixing LiCl 434 g(10.3 mole) (42 g/mole) AlCl₃ 1300 g (9.7 mole) (134 g/mole) Mix 1 moleAlCl₃ to 1.06 mole LiCl in a glass flask with an opening to permit theintroduction of SO₂. Introduction of The flask is evacuated. Next, thedesired amount of SO₂ gas SO₂ is introduced with an over pressure of 1.5bar (by “over pressure” it is meant 1.5 bar over the ambient 1 bar argonpressure), while stirring the salt mixture. When the salt begins todissolve in the SO₂, the pressure of the SO₂ is reduced to an overpressure of 0.5 bar in order to slow the process to permit obtaining aliquid electrolyte having a desired molar ratio of SO₂ to LiAlCl₄ salt.

Other embodiments for producing the electrolyte described herein arefound, for example, in Foster, et al., “New Highly Conductive InorganicElectrolytes—The Liquid S02 Solvates of the Alkali and Alkaline EarthMetal Tetrachloroaluminates,” J. Electrochem. Soc., 135: 2682-2686(1988) and Koslowski, “Röntgenographische undschwingungsspektroskopische Untersuchungen an Solvaten des TypsMAIC14/SO2 (M=Li, Na) und deren Wechselwirkungen mit Aromaten,” DoctoralThesis, University of Hannover/Germany (1980).

Properties of the Cell and its Components

In an embodiment, the electrolyte has, at room temperature, an ionicconductivity of 70 millisiemens/cm.

In a further embodiment, the cells described herein have thickelectrodes (ranges of thickness are set forth above) due to, inter alia,(without being bound by this theory) the ionic conductivity of theelectrolytes described herein. The electrode thickness described hereinis also provided due to, inter alia, (without being bound by thistheory) the porous metal current collector portions described hereinwhich permits access of the electrolyte and active material, forexample, throughout the interior of the porous current collectorstructure. Such thick electrodes permit, for example, decreasedmanufacturing costs (that is, less electrodes may be used per cell).

Also provided, inter alia, by embodiments of the electrolytes describedherein is cell cycle stability, for example, a stable internalresistance of embodiments of the battery cells described herein overmultiple cycles. Without being bound by this theory, it is believed thatthis stability results, inter alia, from the formation of stableelectrode covering layers resulting from the chemical interaction of theelectrolytes and electrodes described herein.

Moreover, in an embodiment, the battery cells described herein, havecell cycle stability (for example, the cell discharge capacity issubstantially constant) over numerous cycles.

In an embodiment, after the first 100 cycles following formation, thecell discharge capacity does not decrease by more than 25% over the next250 cycle increment. In a further embodiment, after 100 cycles followingformation, the discharge capacity will not decrease by more than 25%,20%, 15%, 10%, 5%, 1.5% or 1% over the next 250 cycle increment.

In a further embodiment, the percent loss of discharge capacity iscalculated by comparing the discharge capacity at a given number ofcycles (for example, at 100 cycles following formation as describedabove) to the discharge capacity after a given number of additionalcycles (for example, an increment of 250 cycles as described above). Forexample, for the first increment in the example of the foregoingsentence, if the discharge capacity at 100 cycles is 100 mAh and is 90mAh at 350 cycles, then the percent loss of discharge capacity would by10%. Furthermore, the percent loss of discharge capacity can be measuredat any number of further increments of 250 cycles. Accordingly, in theabove example, the discharge capacity can be measured again at 600cycles and the percent loss of discharge is calculated based on thedifference between the discharge capacity at 350 cycles versus thedischarge capacity at 600 cycles.

In a further embodiment, referring to FIG. 17, the percent loss ofdischarge capacity over 100 cycle increments, beginning at 100 cyclesafter formation and with the last increment ending at approximately9,700 cycles is an average of 0.79%. In a further embodiment, referringto FIG. 17, the percent loss of discharge capacity over 100 cycleincrements, beginning at 100 cycles after formation and with the lastincrement ending at approximately 2,900 cycles is an average of 0.89%.

In a further embodiment, the percent loss of discharge capacity over 100cycle increments, beginning at 100 cycles after formation, is at setforth in any of the 100 cycle increments shown in Table 10 or anycombination such increments.

In a further embodiment, the foregoing charge/discharge cycles arecarried out as follows for each cycle: (1) charging is carried outaccording to the constant current constant voltage (CCCV) method withcharging, for example, at 0.5 C until the cell potential reaches 3.6volts at which time this potential is held constant until the currentreaches 0.1 C, at which time charging is stopped and after a break ofapproximately 10 minutes, (2) discharging is carried out at 0.5 C and isstopped when the cell potential reaches 2.5 volts Approximately 60minutes after step (2) is completed, the foregoing is repeated for thenext cycle. The charge/discharge cycles are carried out at approximately20 C and approximately 1 bar (ambient) pressure.

In a further embodiment, the capacity, in embodiments of the batterycell described herein, per unit area of the positive electrode is atleast 5 mAh/cm², at least 7.5 mAh/cm², at least 10 mAh/cm², at least12.5 mAh/cm² at least 15 mAh/cm², at least 20 mAh/cm² or at least 25mAh/cm.². In a further embodiment, the capacity is from at least 5mAh/cm² to 25 mAh/cm.²

In a further embodiment, more than 90 percent of the theoreticalcapacity of the active material in the positive electrode is obtained inthe cell.

In a further embodiment, the ampacity, in embodiments of the batterycell described herein, per unit area of the positive electrode is atleast 10 mA/cm², at least 50 mA/cm² or at least 150 mA/cm². In a furtherembodiment, the ampacity is from at least 10 mA/cm² to 150 mA/cm². In afurther embodiment, the ampacity is from at least 10 mA/cm² to 200mA/cm². In a further embodiment, the ampacity is from at least 10 mA/cm²to 300 mA/cm².

In a further embodiment, the battery cell is fully charged atapproximately 3.6 volts and the overcharge potential (electrochemicalstability window) of the electrolyte is approximately 4.0 volts. In afurther embodiment, the battery cell is fully charged at a voltage belowthe overcharge potential (electrochemical stability window) of theelectrolyte.

In a further embodiment, the self discharge of the battery cell is abouta five percent loss of charged capacity per month.

Furthermore, in embodiments described herein, the electrolyte is notflammable. For example, SO₂ is not flammable or combustible andaccordingly, electrolyte embodiments containing 100 percent SO₂ andLiAlCl₄ will also be non-flammable and non-combustible. In furtherembodiments, amounts and types of additional ingredients of theelectrolytes are provided that result in the electrolyte beingnon-flammable and non-combustible at predetermined temperatures andpredetermined environmental conditions (e.g., the amount of oxygen towhich the electrolyte is exposed).

In a further embodiment, the cells described herein are in conformancewith the Projectile Test described on page 19 of Underwriter'sLaboratory UL 1642 Standard for Lithium Batteries, Fourth Edition (Sep.19, 2005), such test protocol herein incorporated by reference in itsentirety. That is, when subjected to this test, no part of an explodingcell or battery shall penetrate the wire screen described in the testsuch that some or all of the cell or battery protrudes through thescreen. In a further embodiment, when the test protocol is applied, thecells described herein will not ignite or burn out.

In a further embodiment, the electrolyte in the cells described hereinwill not ignite or combust when the electrolyte or the cell (that is,the cell housing) is placed above a Bunsen burner and contacted with thetip of the Bunsen burner blue flame for at least ten minutes or,alternatively, is exposed to a temperature in excess of 800° C. or atemperature of from °800 to 1000° C. for at least ten minutes.

Separator

As used herein, the term “separator” means (1) a separator, as that termis understood in the lithium ion rechargeable battery field or (2) aninsulator as that term (porous insulator) is described, for example, inU.S. Patent Application Publication No. 20070065714.

Examples of insulator materials include particulate, fibrous, or tubularpore structure materials, formed, for example, from oxides, carbides, orchemically stable silicates. Further examples of insulator materialsinclude glass fiber, e.g., woven glass or glass fleece. In a furtherembodiment, the insulator is inert to the electrolytes described hereinand, in a further embodiment, inert to the overcharge and self dischargeproducts of the cells described herein.

Examples of commercially available woven glass materials are listedbelow in Table 6.

TABLE 6 Company Name Product Name Culimenta HBO029 Norton Pampus GmbH7614 Stottrop Textil Nr.124 Lange + Ritter GmbH 92125 Lange + RitterGmbH 92140 Glasseiden GmbH TG 1000 Glasseiden GmbH TG 430  GlasseidenGmbH TG 100P Interglas 4391 Interglas 92111 Interglas 461 Interglas 2037Interglas 2034 Gröning 2020140 Gröning 2020290 Gröning 30121060

In a further embodiment, the weight per unit area of the woven glassinsulator is approximately 128 g/m², the warp is approximately 47.3fibers/cm, the weft is approximately 21 fibers/cm and the thickness isapproximately 0.12 mm.

In a further embodiment, the insulator is made of woven glass and is inthe form of a pouch 24, in which the positive electrode is placed (FIG.6). In a further embodiment, as shown in FIG. 6, the top of the pouchextends up to a portion of the current collector connector 23. In afurther embodiment, as shown in FIG. 6, the positive electrode in thepouch is configured between two negative electrodes. In a furtherembodiment as shown in FIG. 6, in this configuration, the tabs of thepositive and negative electrodes are on opposite ends.

Housing

In an embodiment, the cell is located in a housing. In a furtherembodiment, the housing is cylindrical or prismatic. The housing is madeof a durable metal, for example, stainless steel. In a furtherembodiment, the housing is designed to withstand the corrosive effectsof the electrolytes. In a further embodiment, the housing is designed tolast for more than 10 years of normal cell use.

In a further embodiment, the housing is prismatic 27 and comprises sixsides, for example, four walls and a top cover 33 and a bottom cover. Ina further embodiment, the top cover 33 comprises 4 ports 32, namely anelectrolyte filing port, a vent port and two electrical ports.

In a further embodiment, an electrically conductive pole 28 is disposedin each electrical port, the pole being disposed in an outer peripheralsurface 29 which engages the cover to occlude the port and whereindisposed between the outer peripheral surface and the pole is aninsulating surface 29. In an embodiment, the foregoing is comprised in aglass-to-metal feedthrough 34 which comprises an electrically conductivepole 28 disposed in a glass insulator 29, which insulates the pole fromthe top cover 33, wherein the insulator is disposed in an outer metalperiphery surface 29 that is sealed, for example, laser welded, to thetop cover 33 and the pole 28 extends through the cover 33 into theinterior of the housing. In a further embodiment, the pole 28 defines aninterior passage allowing communication between the inside and exteriorof the housing. In a further embodiment, the pole provides electricallyconductive communication between the inside and exterior of the housingbut does not contain an interior passage. In a further embodiment, thepole 28 extends through the cover 33 into the interior of the housingand engages a portion of the current collector connector 23.

In a further embodiment, a plug, for example a filling tube 30, isdisposed in the electrolyte filling port. In an embodiment, the plugengages the cover 33 to occlude the port and the plug defines aninterior passage which allows fluid communication between the inside andexterior of the housing.

In a further embodiment, the vent port is occluded with a surface layerdesigned to rupture or release when exposed to a predetermined amount ofpressure. In an embodiment, the surface layer is a metal burst disk, 31.In a further embodiment, the housing is hermetically sealed. In afurther embodiment, the glass-to-metal feedthrough, the electrolytefilling tube and the burst disk are laser welded to the ports of the topcover and the top and bottom covers are laser welded to the wails of thehousing.

Configuration of Electrodes in the Housing and Electrolyte Filling

In an embodiment, as set forth in FIG. 6, two negative electrodes aredisposed on opposing sides of each positive electrode and each positiveelectrode is disposed in a pouch 23 that prevents the physical contactof the positive electrode to either of the negative electrodes.

In a further embodiment, a plurality of positive and negative electrodesin the above configuration are enclosed in a layer which preventsphysical contact between the electrodes and the housing. In anembodiment, the layer is an envelope 25, which is folded over theelectrodes. In a further embodiment, layer 25 a of the envelope isfolded over a negative electrode on one end of the plurality ofelectrodes, layer 25 b of the envelope is folded over a negativeelectrode on the other end of the plurality of electrodes, layers 25 cand 25 d are folded over the exposed sides of the negative electrodesand overlap with layer 25 a to cover the side edge of the negativeelectrode covered by 25 a. In a further embodiment, layers 25 e arefolded over the exposed bottom edge of the negative electrodes.

In a further embodiment, the plurality of electrodes folded in theenvelope 26 is disposed in the housing as shown in FIGS. 8 and 9. In afurther embodiment, the envelope snugly fits the plurality of electrodesinto the housing thereby minimizing any displacement of the positioningof the electrodes in the housing and furthermore preventing physicalcontact between the electrodes and the housing. In a further embodiment,the housing contains 20 positive electrodes and 21 negative electrodes.

In a further embodiment, the housing containing the plurality ofelectrodes folded in the envelope is filled with electrolyte via thefilling tube. In an embodiment, the electrolyte rises to a level belowthe top of the envelopes so that the electrolyte does not directly(other than through the pouch) communicate between the positive andnegative electrode.

In a further embodiment, the cell is filled with electrolyte accordingto processes set forth in U.S. Patent Application Publication No.20070065714 (see for example FIG. 9 of the 20070065714 publication): Ina further embodiment,

-   -   1. A cell housing containing a positive and negative electrode        is evacuated;    -   2. The interior of the housing is filled with gaseous SO₂;    -   3. Steps 1 and 2 are optionally repeated;    -   4. The housing is evacuated;    -   5. A fill opening of the housing is attached gas-tight to a        vessel which contains an electrolyte solution with a        predetermined concentration of SO₂; and    -   6. The electrolyte solution is allowed to flow into the housing        driven by a pressure applied to the electrolyte and by the        vacuum present in the housing.

In a further embodiment, the cell is filled with electrolyte accordingto processes set forth in set forth below in Table 7.

TABLE 7 In cell 1. Cool the cell to −20° C. housing 2. Evacuate the cell(e.g., for 10 min) with a standard containing a vacuum. plurality of 3.Fill the cell with gaseous 100% SO₂ (e.g., for ten electrodes: minutes)at an over pressure of 1 bar. 4. Repeat step 2 and 3 two times. 5.Evacuate the cell. 6. Fill the cell with electrolyte using an overpressure on the electrolyte from 1 to 2.5 bar.

In a further embodiment, the dimensions of the housing, positiveelectrode, pouch and negative electrode are as shown in Table 8:

TABLE 8 Width Thickness Component Height (mm) (mm) (mm) Housing 130 mm130 24.5 Positive 106 mm (not including the 122.5 0.58 Electrode heightof the conductive tab) Pouch 114-118 mm 127.5 0.82 Negative 110-111 mm(not including 127.5 0.32 Electrode the height of the conductive tab)

In a further embodiment, the theoretically calculated capacity of thepositive electrodes in the cell is higher than that of the negativeelectrodes, for example, by 20-30 percent.

Cover Layer Reducing Treatment

In an embodiment, the capacity stability of a cell with at least oneinsertion electrode, for example, an intercalation electrode, areincreased by means of a treatment or pretreatment to reduce the capacityrequired to create stable covering layers on at least one insertionelectrode. There are various embodiments to this end.

A first embodiment is to subject the insertion electrode to atemperature treatment. This applies in particular for carbon electrodes,which are tempered at a temperature of at least 900° C. under exclusionof oxygen (for example, under inert gas) for at least 10, at least 20and or at least 40 hours.

Alternatively or additionally, the capacity required to form stablecovering layers on a negative carbon electrode can be reduced by using agraphite material with a relatively low specific surface area.

According to a further embodiment, the pretreatment to reduce thecovering layers comprises providing the corresponding electrode with athin surface coating.

Such a surface coating can be effected in particular by means of atomiclayer deposition. This method has been used in recent times for numerouspurposes. An overview is given, for example, in the publication, S. M.George “Atomic Layer Deposition: An Overview”, Chem. Rev. 2010, 111-131

The process parameters should be adapted to the requirements of theelectrode. In an embodiment, the negative electrode is pretreated withNO₂-TMA (nitrogen dioxide-trimethylaluminum). This seeds an initialfunctional layer on the carbon, this layer being advantageous forsubsequent ALD treatment. In this context, reference can additionally bemade to G. M. Sundaram et al. “Leading Edge Atomic Layer DepositionApplications”, ECS Transactions, 2008, 19-27.

In a further embodiment, coating by ALD is via a thin layer of Al₂O₃. Ina further embodiment, the ALD layer is formed with SiO₂.

A further embodiment for applying a surface coating suitable forreducing the capacity required to establish a stable covering layers isdip coating. To this end, either the insertion active material intendedfor processing into the electrode or the whole electrode is brought intocontact with a reaction solution that contains starting materialssuitable for the formation of the layer. A temperature treatment is thenperformed to form and harden the layer. The following method can beused, for example.

Isopropanol, water, 1 molar hydrochloric acid andtetraethylorthosilicate are mixed in a mole ratio of 3:1:1:1. Thesolution is kept at room temperature. It is then diluted withisopropanol in the volume ratio 1:1. The electrodes to be treated aredipped in the reaction solution for 30 seconds or, if bubble formationis observed, until bubble formation has stopped. The electrodes are thendried in a drying cabinet at 200° C. without vacuum for 48 hours.

Embodiments of the battery cells described herein are for use in highenergy applications, such as, electric vehicles, energy storage systems,including large scale energy storage system, uninterruptible powersupplies, back up batteries and for certain medical devices. Furtherembodiments of the battery cells described herein are for use in highpower applications, such as, power tools, hybrid vehicles, and certainmedical devices.

In a further embodiment, battery cells described herein are used as apower supply, optionally in combination with other power supplies, andoptionally as either a main or auxiliary power supply for the following:portable electronic devices such as video cameras, digital stillcameras, cellular phones, notebook personal computers, cordlesstelephones, headphone stereos, portable radios, portable televisions andpersonal digital assistants (PDAs), portable home appliances such aselectric shavers, memory devices such as backup power supplies andmemory cards, power tools such as electric drills and electric saws,medical electronic devices such as pacemakers and hearing aids, andmotor vehicles such as electric vehicles, plug in electric vehicles andhybrid vehicles.

In a further embodiment, battery cells described herein are used as anenergy storage system and as a power supply for storing power from andsupplying power to an energy grid.

Referring to the embodiment of FIG. 1, the housing 1 of the rechargeablebattery cell 2 encloses an electrode arrangement 3 comprising aplurality (three in the case shown) of positive electrodes 4 and aplurality (four in the case shown) of negative electrodes 5. Theelectrodes 4, 5 are connected with corresponding terminal contacts 9, 10of the battery by means of electrode leads 6, 7.

The electrodes 4, 5 have a planar shape, i.e., they are shaped as layershaving a thickness which is small relative to their extension in theother two dimensions. They are separated from each other by separators11. The housing 1 of the prismatic cell shown is essentially cuboid, theelectrodes and the wails shown in cross-section in FIG. 1 extendingperpendicularly to the drawing plane and being essentially straight andflat. However, the a further embodiment of the cell can be designed as aspirally wound cell.

The electrodes 4, 5 comprise a current collector element, which is madeof metal and serves to provide the required electronically conductiveconnection of the active material of the respective electrode. Thecurrent collector element is in contact with the active materialinvolved in the electrode reaction of the respective electrode.

In an embodiment, during manufacture of the electrode, the activematerial is incorporated into the porous metal portion of the currentcollector such that it fills the pores of the porous metal, for example,uniformly over, for example, the whole thickness of the porous metal.The active material is then pressed under high pressure, the thicknessafter the pressing operation being in an embodiment, no more than 50% orno more than 40%, of the initial thickness. In a further embodiment, theactive material is distributed essentially homogeneously within theporous metal. “Essentially” is to be construed such that the cellfunction is only slightly impaired by any deviations. In a furtherembodiment, the porous metal extends through at least 70% or at leastapproximately 80%, of the thickness of the electrode.

A portion of an electrode is shown in FIG. 3, in the form of an electronmicroscope image. The electrode material was cooled in liquid nitrogenand then broken, because a cutting operation would have corrupted thestructural features. In spite of certain material damage caused bybreaking 12, features of the structure of the portion of the positiveelectrode are visible in FIG. 3.

For the following Examples, positive electrodes containing LiFePO₄active material were produced as follows.

A paste was produced using the following components:

-   -   94 wt. % LiFePO₄, with carbon surface coating and a mean        particle size approximately 2-3 μm    -   2 wt. % carbon black as conductivity agent    -   4 wt. % THV as binding agent

First the binding agent was dissolved in acetone, then carbon black wasadded to the solution while stirring, and finally the active materialwas added alternately with further solvent, also while stirring.

The paste was then incorporated homogeneously into nickel metal foamhaving an initial porosity of more than 90%, and dried for an hour at 50C. After cooling, the electrode material was pressed by means of acalendar to a thickness of 0.6 mm, starting from an initial thickness of1.7 mm. It was then subjected to a tempering process at 180 C.

Example 1

Pieces with a size of 1 cm² were cut out of the electrode material. Thepieces had a theoretical capacity of approximately 13 mAh. The pieceswere examined in an E-cell with a three-electrode arrangement, in whichthe reference and counter electrode were made of metallic lithium. Theelectrolyte used in the E-cell had the composition of 1.5 moles SO₂. permole of LiAlCl₄.

In order to determine the discharge capacities of the electrodes fordifferent current loads, 40 charging and discharging cycles wereperformed in the E-cells. Charging took place in each case with the samecharging rate of 1 C (“C” indicates that the nominal capacity is chargedor discharged in one hour). Discharging took place after each chargingoperation, with the cells being discharged at the following rates in the40 cycles:

-   -   10 cycles 1 C    -   4 cycles each 2 C, 4 C, 8 C, 10 C, 15 C    -   10 cycles 1 C.

Charging took place up to a voltage of 3.7 V. Discharging ended at avoltage of 3.2 V.

FIG. 11 shows, as mean values over eight experiments, the dischargecapacity Q_(D) in mAh/g as a function of the cycle number. The figureshows the percentage of nominal capacity available the given dischargerates. As shown in the figure, when the cell is discharged with at 10 C,approximately two thirds of the nominal capacity is available.

FIG. 12 summarizes the results illustrated in FIG. 11, showing thedischarge capacity Q_(D) as a function of the discharge rate C (curveA). Curve B in FIG. 11 shows values from the publication, Porcher etal., “Design of Aqueous Processed Thick LiFePO4 Composite Electrodes forHigh-Energy Lithium Battery, J. Electrochem. Soc., A133-A144 (2009).This publication describes the production of, inter alia, electrodeshaving a thickness of 0.2 mm. The electrodes are manufactured with awater-soluble binding agent in aqueous suspension. The resultingcapacity per unit area (“capacity density”) is specified as 3 mAh/cm²,with loading of 20 mg/cm² and an electrode thickness of 200 □m. Themeasurement data plotted in FIG. 12 was taken from FIG. 1 on Page A135of the publication for the “CMC” material. FIG. 12 shows that thecapacity represented by curve B as decreasing with the discharge ratefaster than the capacity shown by Curve A. For a discharge rate of 10 C,for example, the positive electrode described in the publication andshown in Curve B has a discharge capacity of 18 mAh/g compared with 100mAh/g for Curve A. The comparison is summarized by the following Table9:

TABLE 9 Example 1 Porcher et al. Capacity per unit area (mAh/cm²) 13 3Loading with active mass (mg/cm²) 76 20 Electrode thickness (μm) 600 200Specific discharge capacity for 10 C 100 18 (mAh/g)

FIG. 13 shows the values for the resistance R of the positive electrodethat were measured on the E-cells after charging, as a function of thecycle number. In spite of the discharge rates, the resistance of theelectrode remains stable in the range between 0.6 and 0.8 ohms.

For the below Examples 2 and 4, the negative electrode was produced asfollows. A paste was produced using 100% graphite powder. The graphitewas dissolved in acetone while stirring. The paste was incorporatedhomogeneously into a metal foam having an initial porosity of more than90%, and dried for an hour at 50 C. After cooling, the electrodematerial was pressed by means of a calendar to a thickness of 0.3 mm,starting from an initial thickness of 1.7 mm. It was then subjected to atempering process at 1000 C.

Example 2

For this Example, a spirally wound cell of the type Sub-C was produced,the electrodes having a theoretical capacity of 17 mAh/cm² and thepositive electrodes containing LiFePO₄ as active material.

The electrodes were wound into a spiral together with a separatorpositioned between them and placed in the Sub-C housing. This was thenfilled with an electrolyte solution with the composition μ6SO₂ per moleLiAlCl₄. The cell was charged with a charging rate of 0.7 C to 831 mAh.The discharge current was 10 A, corresponding to a discharge rate of 7C. Discharging was stopped at a cell voltage of 2 V and with anextracted capacity of 728 mAh. This corresponds to 88% of the chargedcapacity.

Example 3

Using a positive electrode produced as set forth above and a positiveelectrode containing lithium cobalt oxide as the active material, butotherwise having corresponding features, the dependence of the capacityon the number of charging and discharging cycles (each with 1 C) in anE-cell was determined.

FIG. 14 shows the results obtained using an SO₂ electrolyte containing1.5 mole SO₂ per mole of conductive salt (lithium tetrachloroaluminate).The discharge capacity Q_(D) in percent of the theoretical value isplotted against the number of charging and discharging cycles performed,where curve A relates to the LiFePO₄ electrode and curve B to thelithium cobalt oxide electrode. The curves show the amount of thetheoretical capacity obtained with the LiFePO₄ electrodes, whereas onaverage only around 60% of the theoretical capacity is shown in curve B.

FIG. 15 shows the results of an experiment that differed from theexperiment that served as a basis for FIG. 14 with respect to theconcentration of the conductive salt in the electrolyte. In this case itwas 4.5 mole SO₂ per mole of LiAlCl₄. The figure shows that the percentdecrease in capacity for the LiFePO₄ electrode (curve A) versus thelithium cobalt oxide electrode (curve B).

Example 4

FIG. 16 shows the results of an experiment in an HPCM cell (two negativeelectrodes and one positive electrode), with the positive electrodecontaining LiFePO₄ with a theoretical capacity of 19 mAh/cm² (curve A),compared with a HPCM cell with a positive electrode based on lithiumcobalt oxide (curves B), but otherwise having corresponding features.For both curves, the electrolyte contained 6 moles of SO₂ per molLiAlCl₄.

The discharge capacity Q_(D) in percent of the nominal value is plottedagainst the number of cycles. After an initial decrease, the extractablecapacity for the cell is substantially constant versus the comparisoncell.

FIG. 17 shows the results of a long-duration test with a cell of thetype used in FIG. 9, curve A, where the extracted capacity Q_(D) isagain plotted against the number of cycles. The figure shows approx.9,700 cycles, in which the reduction in the extractable capacity per 100cycles as set forth in Table 10 below.

Table 10 shows the reduction in capacity per 100 cycles for the datashown in the curves of FIG. 16 (curve A) and FIG. 17. The incrementsbeginning at 3100 are shown in Table 10 as 200 cycle increments but thedelta is calculated based on 100 cycle increments (that is the delta isaveraged over the two 100 cycle increments).

TABLE 10 cycle discharge capacity (% of delta between 100 number max.discharge capacity) cycle increments 100 75.50% 5.70% 200 69.80% 3.20%300 66.60% 2.30% 400 64.30% 1.60% 500 62.70% 1.50% 600 61.20% 1.20% 70060.00% 1.00% 800 59.00% 0.80% 900 58.20% 0.50% 1000 57.70% 0.70% 110057.00% 0.50% 1200 56.50% 0.50% 1300 56.00% 0.50% 1400 55.50% 0.50% 150055.00% 0.50% 1600 54.50% 0.50% 1700 54.00% 0.30% 1800 53.70% 0.50% 190053.20% 0.40% 2000 52.80% 0.30% 2100 52.50% 0.30% 2200 52.20% 0.40% 230051.80% 0.30% 2400 51.50% 0.30% 2500 51.20% 0.40% 2600 50.80% 0.10% 270050.70% 0.40% 2800 50.30% 0.30% 2900 50.00% 0.20% 3000 49.80% 0.30% 310049.50% 0.50% 3300 49.00% 0.50% 3500 48.50% 0.50% 3700 48.00% 0.50% 390047.50% 0.50% 4100 47.00% 0.50% 4300 46.50% 0.50% 4500 46.00% 0.50% 470045.50% 0.00% 4900 45.50% 0.50% 5100 45.00% 0.30% 5300 44.70% 0.70% 550044.00% 0.50% 5700 43.50% 0.50% 5900 43.00% 0.50% 6100 42.50% 0.50% 630042.00% 1.00% 6500 41.00% 0.70% 6700 40.30% 0.50% 6900 39.80% 0.10% 710039.70% 0.40% 7300 39.30% 0.50% 7500 38.80% 0.63% 7700 38.17% 0.50% 790037.67% 2.00% 8100 35.67% 0.34% 8300 35.33% 0.50% 8500 34.83% 1.33% 870033.50% 0.50% 8900 33.00% 0.33% 9100 32.67% 0.67% 9300 32.00% 0.33% 950031.67% 0.34% 9700 31.33% —

Example 5

FIG. 19 shows the percent of maximum discharge capacity versus cyclenumber for HPCM cells containing positive electrodes with lithium cobaltoxide as the active material and negative electrodes in accordance withthe description above in an electrolyte having mole ratios of 1.0, 1.5,3.0, 4.5, and 6.0 SO₂ per mole of LiAlCl₄ and shows a decreasing trendwith increasing amounts of SO₂ per mole of LiAlCl₄. The breaks in thecurve for 3.0 SO₂ reflect a failure of a cell(s) in the experiment.

FIG. 20 shows the percent of maximum discharge capacity versus cyclenumber for HPCM cells containing positive electrodes with LiFePO₄ as theactive material and negative electrodes in accordance with thedescription above in an electrolyte having mole ratios of 1.5, 4.5, 6.0,10.0 and 22.0 SO₂ per mole of LiAlCl₄ and shows an increasing and thenstabilized trend as amounts of SO₂ per mole of LiAlCl₄ are increased.The breaks in the curves for 22.0, 6.0 and 10.0 SO₂ indicate a failureof cell(s) in the experiment.

Example 6

Table 11 below lists the amount of capacity consumed, based on apercentage of theoretical capacity, to form a stable SEI layer atincreasing amounts of SO₂ per mole of LiAlCl₄ for cells with LiFePO₄positive electrodes compared to lithium cobalt oxide positiveelectrodes. With both active materials, a decreased amount of capacityis consumed with the increase in SO₂ per mole of LiAlCl₄ from 1.00 to6.00.

TABLE 11 SEI formation capacity (% of the theoretical SO₂ per molecapacity of the positive electrode) LiAlCl₄ LiCoO₂ LiFePO₄ 1.00 23.5226.96 1.50 21.16 22.58 3.00 21.85 21.52 4.50 18.73 18.94 6.00 15 16.98

Example 7

FIG. 18 shows the results of an experiment with the following electrodematerials:

-   -   Curve A negative electrode without cover-layer-reducing        pretreatment.    -   Curve B negative electrode where the active material was        pretreated by means of dip coating with formation of an SiO₂        layer, before incorporation in the electrode.    -   Curve C negative electrode that was pretreated as a whole by        means of dip coating with formation of an SiO₂ layer.

The three experimental electrodes were examined in an E-cell. Duringcharging of the electrode, the voltage U against lithium was plotted involts against the charge state Q, as fraction of the nominal capacityQ_(N). The three graph groups illustrated show the results of severalexperiments in each case with the above-described electrodes. It isevident that the capacity loss for the two pretreated electrodes is lessthan for the untreated electrode, the electrode pretreated in itsentirety being slightly better than the other pretreated electrode. Itis noted that the data in Curve C has not yet been reproduced in an HPCMcell.

Battery cells with SO₂ electrolytes are described in the followingdocuments which are herein incorporated by reference in their entirety,for example:

-   U.S. Pat. No. 5,213,914-   WO 00/44061 and U.S. Pat. No. 6,709,789-   WO 00/79631 and U.S. Pat. No. 6,730,441-   WO 2005/031908 and US 2007/0065714-   L. Zinck et al. “Purification process for an inorganic rechargeable    lithium battery and new safety concepts”, J. Appl. Electrochem.,    2006, 1291-1295-   WO 2008/058685 and US Patent Application 2010/0062341 WO 2009/077140

All the patent documents and other publications cited herein are herebyincorporated by reference in their entirety.

1. A battery cell, comprising: a housing, a positive electrode, anegative electrode and an electrolyte, wherein the electrolyte comprisesSO₂ and a conductive salt, wherein the positive electrode comprises acompound of the formula Li_(x)M′_(y)(XO₄)_(a)F_(b) (I), which compoundis optionally doped, wherein M′ is at least one metal selected from thegroup consisting of the elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, Xis selected from the group consisting of the elements P, Si and S, x isgreater than 0, y is greater than 0, a is greater than 0 and b isgreater than or equal to 0, wherein the sum of positive charges in thecompound equals the sum of negative charges, wherein the positiveelectrode further comprises a current collector having a first portioncomprising a porous metal which has a first and second surface and athickness located there between and comprises a plurality of porescontaining the compound that extend at least partially through thethickness, wherein at least some of the pores have void spacesaccessible to the electrolyte and wherein the battery cell is arechargeable lithium ion battery cell.
 2. A battery cell, comprising: ahousing, a positive electrode, a negative electrode and an electrolyte,wherein the positive electrode comprises LiFePO₄ which is optionallydoped, wherein the electrolyte comprises SO₂ and a conductive salt,wherein the positive electrode further comprises a current collectorhaving a first portion comprising a porous metal which has a first andsecond surface and a thickness located there between and comprises aplurality of pores containing the compound that extend through thethickness, wherein at least some of the pores have void spacesaccessible to the electrolyte and wherein the battery cell is arechargeable lithium ion battery cell.
 3. A battery cell, comprising: ahousing, a positive electrode, a negative electrode and an electrolyte,wherein the positive electrode comprises LiFePO₄ which is optionallydoped, the electrolyte comprises SO₂ and a conductive salt, wherein theSO₂ is in an amount greater than 40 weight percent of the weight of theelectrolyte and wherein the battery cell is a rechargeable lithium ionbattery cell.
 4. A battery cell comprising a housing, a positiveelectrode, a negative electrode and an electrolyte, wherein the positiveelectrode comprises LiFePO₄ which is optionally doped, wherein theelectrolyte comprises SO₂ and a conductive salt, wherein organicmaterial is in an amount less than 60 weight percent of the weight ofthe electrolyte and wherein the battery cell is a rechargeable lithiumion battery cell.
 5. A battery cell comprising a housing, a positiveelectrode, a negative electrode and an electrolyte, wherein the positiveelectrode comprises LiFePO₄ which is optionally doped, wherein theelectrolyte comprises SO₂ and a conductive salt, wherein the electrolytecomprises at least 3 moles SO₂ per mole of conductive salt, and whereinthe battery cell is a rechargeable lithium ion battery cell.
 6. Thebattery cell according to claim 1, wherein after the first 100 cycles ofcharging and discharging following formation, the cell dischargecapacity does not decrease by more than 25 percent over the next 250cycles, wherein the cell is charged at a current of 0.5 C until the cellpotential reaches 3.6 V at which time the potential of 3.6 V is heldconstant until the current reaches 0.1 C, at which time the charging isstopped and after a delay of approximately 10 minutes, the cell isdischarged at a current of 0.5 C and the discharging is stopped when thecell potential reaches 2.5 V, and wherein after a delay of approximately60 minutes after the discharging is stopped, (1) and (2) are repeatedfor the next cycle, wherein the charge and discharge cycles are carriedout at approximately 20 C and approximately 1 bar (ambient) pressure. 7.The battery cell of claim 1, wherein the plurality of pores furthercontain a compound selected from the group consisting of a conductiveagent, a binding agent, and a lithium halogenide.
 8. The battery cell ofclaim 1, wherein the plurality of pores extend through the entirethickness.
 9. The battery cell of claim 1, wherein the current collectorfurther comprises a connector portion in conductive contact with theporous current collector.
 10. The battery cell of claim 1, wherein thepositive electrode has a thickness of at least 0.25 mm.
 11. The batteryof cell of claim 1, wherein the positive electrode has a thickness offrom 0.25 mm to 1.0 mm.
 12. The battery cell according claim 1, whereinthe positive electrode comprises a quantity of active material per unitarea of at least 30 mg/cm².
 13. The battery cell according claim 1,wherein the positive electrode comprises a quantity of active materialper unit area of from 30 mg/cm² to 180 mg/cm².
 14. The battery cellaccording to claim 1, wherein the positive electrode is porous and has aporosity of no more than 50%
 15. The battery cell according to claim 1,wherein the negative electrode has a thickness of at least 0.2 mm. 16.The battery cell according to claim 1, wherein the negative electrodehas a thickness of from 0.2 mm to 0.8 mm.
 17. The battery cell accordingto claim 1, wherein the positive electrode comprises a binding agent inan amount of no more than 10 wt. % of the active material.
 18. Thebattery cell according to claim 1, wherein the negative electrodecomprises carbon for inserting lithium ions.
 19. The battery cellaccording to claim 1, wherein the negative electrode comprises aquantity of active material of at least 10 mg/cm².
 20. The battery cellaccording to claim 1, wherein the negative electrode comprises aquantity of active material per unit area of from 10 mg/cm² to 100mg/cm².
 21. The battery cell according to claim 1, wherein the negativeelectrode is porous and its porosity is no more than 50%.
 22. Thebattery cell according to claim 1, wherein the negative electrodecomprises a porous metal portion and binding agent contained therein andthe binding agent is in an amount of no more than 5 wt. % of the weightof the porous metal portion of the negative electrode.
 23. The batterycell according to claim 1, wherein the electrolyte comprises at least 3moles SO₂ per mole of conductive salt.
 24. The battery cell according toclaim 1, wherein the electrolyte comprises from 3 to 220 moles SO₂ permole of conductive salt.
 25. The battery cell according to claim 1,wherein the conductive salt comprises lithium tetrachloroaluminate. 26.The battery cell according to claim 1, wherein the positive electrodehas a current carrying capacity of at least 10 mA/cm².
 27. The batterycell according to claim 1, wherein the positive electrode has anampacity per unit area of from 10 mA/cm² to 150 mA/cm²
 28. The batterycell according to claim 1, wherein lithium chloride is mixed with activemetal of the positive electrode.
 29. The battery cell according to claim1, wherein the positive and/or negative electrode is treated to reducecovering layers by means of applying a surface coating to the electrode.30. A method for producing a positive electrode for a lithium ionrechargeable battery, comprising: providing a paste mass comprisingLiFePO₄, optionally with admixture of a binding agent or aconductivity-improving material; homogeneously incorporating the pastemass into a three-dimensional porous metal current collector; andpressing the three-dimensional metal current collector comprising thepaste mass in such a manner that its thickness is reduced.
 31. Anelectrode produced according to the method of claim
 23. 32. The batterycell of claim 1, wherein the electrolyte comprised therein will notignite or combust when a battery comprising the cell is placed above aBunsen burner and contacted with the tip of a blue flame of the Bunsenburner for at least 10 minutes.
 33. A motor vehicle power supply,comprising the battery cell of claim
 1. 34. An energy storage system,comprising the battery cell of claim 1.